Depletion and Conservation of Natural Resources - Wetlands—fragile Ecosystems

percent water species land

Marshes, swamps, bogs, estuaries, and bottomlands comprise about 5 to 9 percent of the 48 contiguous states and about 40 percent of Alaska. Although these terms refer to specific biosystems with sometimes very distinctive characteristics, they are commonly grouped together under the name "wetlands." Wetlands provide a vivid example of the dynamic, yet fragile interactions that create, maintain, and repair the world's ecological system. Unfortunately, the fate of many wetlands can also offer concrete evidence of the harmful consequences of human activities that are carried out without regard for, and often without knowledge of, the relationship of each part of the ecosystem to the whole.

Once regarded as useless swamps, good only for breeding mosquitoes and taking up otherwise valuable space, wetlands have become the subject of increasingly heated debate. Many people want to use them for commercial purposes such as agricultural and residential development. Others want them left in their natural state because they believe that wetlands and their inhabitants are indispensable parts of the natural cycle of life on Earth.

What Are Wetlands?

"Wetlands" is a general term used to describe areas that are always or often saturated by enough surface or groundwater to sustain vegetation that is typically adapted to saturated soil conditions, such as cattails, bulrushes, red maples, wild rice, blackberries, cranberries, and peat moss. The Florida Everglades and the coastal Alaskan salt marshes are examples of wetlands, as are the sphagnum-heath bogs of Maine. Because some varieties of wetlands are rich in minerals and nutrients and provide many of the advantages of both land and water environments, they are often dynamic systems that teem with a diversity of species, including many insects—a basic link in the food chain.

Wetlands are generally located along sloping areas between uplands and deep-water basins such as rivers, although they may also form in basins far from large bodies of water. Of the 90 million acres of wetlands in the lower 48 states, almost all (95 percent) are inland, freshwater areas; the remaining 5 percent are coastal saltwater wetlands. Alaska is estimated to have more than 200 million acres of wetlands.

There are several distinct forms of wetlands, each with its own unique characteristics. The main factors that distinguish each type of wetland are location (coastal or inland), source of water (precipitation, rivers and streams, groundwater), salinity (freshwater or saltwater), and the dominant type of vegetation (peat mosses, soft-stemmed, or woody plants). Wetlands are a continuum in which plant life changes gradually from predominantly aquatic to predominantly upland species. The difficulty in defining the exact point at which a wetland ends and upland begins results in much of the confusion as to how wetlands should be regulated.

The Many Roles of Wetlands

Experts have understood some of the functions of wetlands for many years. Other purposes have come to light more recently.


Wetlands are a source of food and habitat for numerous game and nongame animals. For some species of waterfowl and freshwater and saltwater fish, wetlands are essential for nesting and breeding. About one in five plant and animal species listed as endangered by the U.S. government depend on wetlands for their survival. Two-thirds of the species of Atlantic fish and shellfish that humans consume depend on wetlands for some part of their life cycle, as do nearly half of all species listed as endangered or threatened.

Coastal marshes and some inland freshwater wetlands boast some of the highest rates of plant productivity of any natural ecosystem, thus supporting abundant animal populations within the food chain. After a plant dies nearly 70 percent of it breaks down and is flushed into adjacent waters where it can be consumed by fish and shellfish.

Inland wetlands also serve as way stations for migrating birds. The 30,000-acre region in the north central United States and south central Canada, for example, provides a resting place and nourishment for nearly half of the more than 800 species of protected migratory birds (which individually number in the millions) during the migration season. Without this stopover the flight to their Arctic breeding grounds would be impossible.


Wetlands can temporarily or permanently trap pollutants such as excess nutrients, toxic chemicals, suspended materials, and disease-causing microorganisms—thus cleansing the water that flows over and through them. Some pollutants that become trapped in wetlands are biochemically converted to less harmful forms; other pollutants remain buried there; still others are absorbed by wetland plants and either recycled through the wetland or carried away from it. (See Figure 9.5.)


Between 60 and 90 percent of the United States' commercial fish species spawn in coastal wetlands. More than one-half of the country's seafood catch depends on wetlands during some part of their life cycle.


Isolated and floodplain wetlands can reduce the frequency of flooding in downstream areas by temporarily storing runoff water. For example, the Cache River watershed in southern Illinois retains about 8.4 percent of the watershed's total runoff during flooding.


Because of their density of plant life, wetlands can dramatically lessen shoreline erosion caused by large waves and major flooding along rivers and coasts.


Many popular recreational activities, including fishing, hunting, and canoeing, occur in wetlands. FIGURE 9.5
Wetlands' contribution to improving water quality and reducing storm water runoff
In addition wetland areas provide open space, an important but increasingly scarce commodity.

History of Wetlands Use

Early Americans considered wetlands nature's failure, a waste in nature's economy. They sought not to preserve nature in its original form but to increase the efficiency of natural processes. In an agricultural economy, land unable to produce crops or timber was considered worthless. Many Americans began to think of draining these lands, an undertaking requiring government funds and resources.

In the nineteenth century state after state passed laws to drain (reclaim) wetlands by the formation of drainage districts and statutes. Coupled with an agricultural boom and technological improvements, reclamation projects multiplied in the late nineteenth and early twentieth centuries. The farmland under drainage doubled between 1905 and 1910 and again between 1910 and 1920. By 1920 state drainage districts in the United States encompassed an area larger than Missouri.

After the Great Depression of the 1920s and 1930s, programs such as the Works Progress Administration and the Reconstruction Finance Corporation encouraged wetland conversion to form land for urban development. In 1945, at the end of World War II, the total area of drained farmland increased sharply.

In the final few decades of the twentieth century, however, conservationists and the courts have challenged reclamation. Where drainage was once thought to improve the look of the land, today it is more likely to be seen as degrading it. Wetlands turned out not to be wastelands but the conservationist's ideal—systems efficient in harnessing the Sun's rays to feed the food chain. Studies have shown that wetlands have far greater value for flood protection than for their potential agricultural use.


When the first Europeans arrived in America, there were an estimated 215 million acres of wetlands. By the beginning of the twenty-first century only about 90 million or so acres remained. In the 200 years since the birth of the United States, more than 50 percent of the wetlands in the 48 contiguous states have been taken over for agriculture, mining, forestry, oil and gas extraction, and urbanization. Some loss resulted from natural causes such as erosion, sedimentation (the buildup of soil by the settling of fine particles over a long period of time), subsidence (the sinking of land because of diminishing underground water supplies), and a rise in the sea level. However, 95 percent of the losses since the 1970s have been caused by humans, especially by the conversion of wetlands to agricultural land. (See Figure 9.6.)

Eighty percent of the wetland conversions were for agricultural purposes; 8 percent for the construction of impoundments (water confined within an enclosure) and large reservoirs; 6 percent for urbanization; and 6 percent for other purposes such as mining, forestry, and road construction.

More than half (56 percent) the losses of coastal wetlands resulted from dredging for marinas, canals, port development, and, to some extent, from natural shoreline erosion. Urbanization accounted for 22 percent, 14 percent was from creating beaches, 6 percent from natural or human-made transitions of saltwater wetlands to freshwater wetlands, and only 2 percent from agriculture.

California, Ohio, Iowa, Indiana, and Missouri have lost almost all their wetlands. The Fish and Wildlife Service estimates that the United States is losing more than 250,000 acres each year—about 30 acres every hour. Developers have discovered that many of the most tempting sites for new housing or shopping centers are wetlands.

The conversion of wetlands causes the loss of natural pollutant sinks (repositories). As water floods into wetlands from rivers and streams, the loss in velocity causes sediments and their absorbed pollutants to settle out in the wetland before they can enter other water bodies. In the United States artificial wetlands have been proposed as a means of controlling pollution from nonpoint sources. The dramatic decline in wetlands globally suggests not only loss of habitat but also diminished water quality.

One of the largest wetlands in the United States is the Everglades of south Florida. The fresh water that used to flow naturally into this ecosystem has been diverted by decades of canal building. According to Nicole Duplaix in "South Florida Water: Paying the Price" (National Geographic, July 1990), drainage changes implemented since 1920 to create farmland or housing had dried out half of the Everglades National Park, and left the rest heavily polluted. Scientists are studying the complex water flow problems in this area and are working to restore some natural drainage characteristics to the Everglades. According to the Comprehensive Everglades Restoration Plan (CERP) Web site (, as of 2002 some limited progress had been made and environmental improvements were expected by 2010.

Concern over Property Rights

The dispute over wetlands regulation reflects Americans' ambivalence when private property and public rights intersect, especially since three-fourths of the nation's FIGURE 9.6
Number of wetland acres lost annually, 1950s–70s, 1970s–80s, and 1990s
wetlands are owned by private citizens. In recent years many landowners have complained that wetland regulation devalued their property by blocking its development. They argue that efforts to preserve the wetlands have gone too far, citing instances where a small wetland precludes the use of much larger surrounding areas. Some large landowners have long opposed any federal (and state and local) powers to protect resources such as wetlands that might limit their land use options.

Another policy question of concern to the public is the right of the federal government to take property without compensation. The "takings" clause of the Constitution (the Fifth Amendment) provides that, when private property is taken for public use, just compensation must be paid to the owner. Owners claim that when the government—through its laws—eliminates some uses for their land, the value is decreased and they should, therefore, be paid for the loss.

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